1. Field of the Invention
The present invention relates to a toner quantity measuring device, a method of measuring toner quantity and an image forming apparatus.
2. Description of the Prior Art
Image forming apparatuses such as copiers and printers, which employ electrophotography, are designed to form toner images on a recording medium like a paper through a series of image forming processes including an electrifying step, an exposure step, a developing step, a transfer step and a fixing step.
At the developing step, as an example, under the state that a developing roller, which carries toner, is caused to make contact with or closely positioned to a photosensitive member carrying an electrostatic latent image, the electrified toner on the developing roller is applied to the latent image, thereby visualizing the latent image as a toner image. At this moment, if the quantity of the toner on the developing roller is not kept uniform within a permissible extent in a longitudinal direction of the developing roller, there may arise such an instance that the quantity of the toner applied is subject to unwanted variation or surplus-and-shortage, which in turn makes it impossible to perform the developing process in a desired manner. In order to avoid this situation, at the final stage in a production line, the quantity of the toner on the developing roller is measured to determine whether the toner quantity measured remains within a predetermined range or not.
Conventionally, there is generally known a toner quantity measuring method wherein the toner quantity is measured by way of causing the toner in a predetermined area of the developing roller to adhere to an adhesive tape having known weight, and then measuring the increased weight of the adhesive tape on which the toner is stuck.
However, such a method involves a drawback in that the task of sticking and peeling off the adhesive tape with respect to the developing roller has to be carried out manually and thus a prolonged period of time is required to measure the toner quantity, which results in an increased manufacturing cost of the products.
In addition, this method lacks consideration for environment because the adhesive tape is doomed to be wastes at the end of the measuring process.
Moreover, due to the fact that the adhesive tape is brought into contact with the developing roller at the time of measurement, the developing roller may suffer from scratches and the adhesive agent of the tape may be left on the developing roller. This will give rise to a possibility of reducing the image quality of the image forming apparatus.
Still further, in the event that the toner on the developing roller has an increased quantity and greater thickness, it becomes difficult to have the toner in the target area adhere to the adhesive tape in its entirety, and thereby a difficulty may be encountered in obtaining accurate outcome of measurement.
In addition to the method referred to above, there is known a method using a non-woven fabric having known weight, as another example of the toner quantity measuring method wherein the toner quantity is measured by adhesion of the toner (see, for example, paragraph 37 of Japanese Laid-open Patent Publication No. 8-17920). This method also has the same problems as in the prior art method set forth above.